Two agents, denosumab (Xgeva) and zoledronic acid (Zometa), are currently approved to help reduce the incidence of skeletal-related events (SREs) in patients with metastatic breast cancer (MBC). Each of these agents has a unique set of clinical parameters.

Certain factors make the administration of denosumab more convenient, such as the agent being a subcutaneous injection rather than intravenous, like zoledronic acid, notes Joyce A. O'Shaughnessy, MD. Additionally, renal toxicity is not a concern with denosumab, as it is with zoledronic acid. However, the clinical trials investigating denosumab only provide data for a few years of administration. As a result, the safety and efficacy for the extended use of this agent remains unclear.

Osteonecrosis of the jaw (ONJ) is a low frequency side effect for both of these treatments. As patients remain on these agents longer, the risk of developing this side effect increases. In many situations, ONJ occurs beyond two years; as a result, taking a treatment break may effectively reduce the risk of developing this side effect.

Before the approval of these agents patients were regularly admitted to the hospital for hypocalcaemia, points out Andrew D. Seidman, MD. While ONJ can be severe, these agents have made a substantial impact on bone health for patients with MBC.